This invention relates to a suspension mechanism for a vehicle, such as a bicycle, and, more particularly, to a suspension apparatus that imparts a forward movement inducing moment to the bicycle after encountering a force compressing the suspension apparatus.
Bicycle suspension mechanisms provide a spring mechanism between the rider and the wheels of the bicycle to isolate the rider from bumps and irregularities on the path being traveled. While suspension mechanisms, particularly rear wheel suspension mechanisms, are not new in the design and manufacture of bicycles, significant interest has been generated recently with the increased popularity of mountain bikes, typically used for off-highway travel. A properly designed rear suspension mechanism will provide a greater level of comfort and energy efficiency for the rider, as well as improve handling capabilities for the bicycle, all of which can be of significant importance particularly when such bicycles are raced over uneven ground.
Most bicycle suspension mechanisms utilize a pivot device to provide a greater range of movement for the mechanism without transmitting pedal-induced movement to the mechanism. Shock absorbers are usually provided to smooth out the movement of the suspension mechanism, such as is found in U.S. Pat. No. 5,899,480, issued to Horst Leitner on May 4, 1999. A pivotless rear suspension system for bicycles can be found in U.S. Pat. No. 6,406,048, issued to John Castellano on Jun. 18, 2002. Such suspension mechanisms, whether formed with or without pivots, connect to the axle of the rear wheel which corresponds to the axis of rotation of the rear drive wheel of the bicycle. Accordingly, the forces encountered by the rear wheel traveling over uneven terrain are transmitted to the suspension mechanism which effectively absorbs the upward force exerted on the rear wheel axle and transmits any remaining force directly back to the rear wheel axle.
In U.S. Pat. No. 6,092,823, issued to James Busby on Jul. 25, 2000, a flexible joint is disclosed for use in a bicycle frame. The flexible joint includes a flat plate received within a pair of opposing adapters that are in turn mounted in respective ends of the bicycle frame tubing. The flat plate facilitates bending in a specified plane, but resists torsional movement along the longitudinal axis of the joint. These flexible joints are replacements for the pivot devices incorporated into the rear suspension system of the bicycle, allowing movement of one member relative to another along a longitudinal axis, while limiting the torsional movement of one frame member relative to the other.
None of the known bicycle rear suspension systems provide any function for the operation of the bicycle other than to isolate the rider from an uneven terrain. The storing and releasing of energy from rear suspension spring mechanisms could be advantageously utilized to enhance the momentum of the bicycle, even if only minutely. When such bicycles are raced over the course of several hours of time and many miles of uneven terrain resulting in the operation of the suspension mechanism to improve the ride characteristics of the bicycle, even minute assistance in the generation of a forward movement inducing moment would result in a significant advantage. Accordingly, it would be desirable to provide a rear suspension system for a bicycle that would result in the transmission of a moment at the rear drive wheel of the bicycle as the suspension system operates to absorb forces to isolate the rider from the bumps and terrain irregularities encountered on the trail.
It is an object of this invention to overcome the aforementioned disadvantages of the prior art bicycle rear suspension systems to provide a rear suspension system that imparts a moment at the rear drive wheel of the bicycle.
It is another object of this invention to provide an aesthetically pleasing rear suspension system.
It is still another object of this invention to provide a rear suspension system that utilizes a parabolic swing arm member to define a semi-elliptical shape for the apparatus.
It is still another object of this invention to provide a flexor within the parabolic shape of the rear suspension apparatus to focus the release of energy stored during the compression of the apparatus.
It is a feature of this invention that the flexor is located at or below and forwardly of the axis of rotation of the rear drive wheel of the bicycle.
It is another feature of this invention that the flexor element imparts a moment to contribute to the forward momentum of the bicycle when the flexor element releases energy stored therein during compression of the rear suspension mechanism.
It is an advantage of this invention that the position of the flexor within the parabolic swing arm of the rear suspension mechanism results in the creation of a forward movement inducing moment at the rear wheel of the bicycle when the rear suspension mechanism releases energy.
It is still another feature of this invention that the flexor can be formed from a carbon fiber/epoxy composite or other materials, such as titanium, to provide a lightweight flexor element that has excellent shape retention properties to provide the ability to store energy during compression of the rear suspension mechanism.
It is yet another object of this invention to combine the properties of pivoted and pivotless rear suspension mechanisms for bicycles to provide an improved rear suspension system that has a minimum of pivot devices, yet permits an efficient and effective suspension to smooth the ride characteristics for the rider.
It is still another advantage of this invention that the parabolic swing arm in the rear suspension mechanism can be adapted to incorporate a shock absorber to dampen the compression of the rear suspension mechanism.
It is yet another feature of this invention that the parabolic swing arm is adaptable to several different shock absorber configurations and orientations.
It is still another feature of this invention that the flexor is formed with a thin portion at the center of the flexor that permits the flexor to bend.
It is yet another object of this invention to mount the parabolic swing arm member such that the axis of rotation of the rear wheel is positioned proximate to the vertex of the parabolic shape to position the flexor element at or below the central axis of the parabolic shape to create a moment arm between the force exerted by the flexor element upon release of stored energy and the axis of rotation of the rear wheel.
It is another feature of this invention that the axis of rotation of the rear wheel can be oriented in alignment with the central axis of the parabolic shape of the rear suspension swing arm.
It is yet another advantage of this invention that the parabolic swing arm is oriented to spread apart as the rear suspension system operates to store energy in the flexor element.
It is a further feature of this invention that the flexor element can be formed as a separate member that is assembled into the perimeter of the parabolic swing arm or as an integral part of the parabolic swing arm.
It is yet another object of this invention to provide a connection linkage for the parabolic swing arm that forces divergence of the upper and lower legs of the swing arm when pivoted upwardly to absorbs forces encountered by the rear wheel engaging bumps and/or irregularities in the surface of the ground.
It is still a further feature of this invention to mount the connection linkage for the upper leg of the parabolic swing arm to pivot about a different pivot center than the swing arm to cause divergence of the upper and lower legs of the swing arm.
It is a further object of this invention to provide a rear suspension mechanism for a bicycle that imparts a forward motion-inducing moment to the bicycle, which is durable in construction, inexpensive of manufacture, carefree of maintenance, facile in assemblage, and simple and effective in use.
These and other objects, features and advantages are accomplished according to the instant invention by providing a bicycle rear suspension mechanism that imparts a forward movement inducing moment about the rotational axis of the rear wheel during the operation of the suspension mechanism. A parabolic swing arm that is mounted such that the axis of rotation of the rear wheel is positioned proximate to the vertex, and preferably in alignment with the central axis, of the parabolic shape. A flexor element is formed into the perimeter of the parabolic swing arm at a location below the central axis of the parabolic shape and below and forwardly of the axis of rotation of the rear wheel. A shock absorber can be connected to the upper rocker arm to dampen the operation of the suspension mechanism. The release of stored energy in the flexor element directs a resultant force offset by a moment arm from the axis of rotation of the rear wheel to contribute to the forward momentum of the bicycle.